namespace Oni.Metadata
{
    internal class CompareVisitor : MetaTypeVisitor
    {
        private readonly BinaryReader reader1;
        private readonly BinaryReader reader2;
        private bool equals = true;

        public CompareVisitor(BinaryReader reader1, BinaryReader reader2)
        {
            this.reader1 = reader1;
            this.reader2 = reader2;
        }

        public bool AreEquals => equals;

        public override void VisitByte(MetaByte type) => equals = (reader1.ReadByte() == reader2.ReadByte());
        public override void VisitInt16(MetaInt16 type) => equals = (reader1.ReadInt16() == reader2.ReadInt16());
        public override void VisitInt32(MetaInt32 type) => equals = (reader1.ReadInt32() == reader2.ReadInt32());
        public override void VisitUInt32(MetaUInt32 type) => equals = (reader1.ReadUInt32() == reader2.ReadUInt32());
        public override void VisitInt64(MetaInt64 type) => equals = (reader1.ReadInt64() == reader2.ReadInt64());
        public override void VisitUInt64(MetaUInt64 type) => equals = (reader1.ReadUInt64() == reader2.ReadUInt64());
        public override void VisitFloat(MetaFloat type) => equals = (reader1.ReadSingle() == reader2.ReadSingle());
        public override void VisitColor(MetaColor type) => equals = (reader1.ReadInt32() == reader2.ReadInt32());
        public override void VisitRawOffset(MetaRawOffset type) => equals = (reader1.ReadInt32() == reader2.ReadInt32());
        public override void VisitSepOffset(MetaSepOffset type) => equals = (reader1.ReadInt32() == reader2.ReadInt32());
        public override void VisitPointer(MetaPointer type) => equals = (reader1.ReadInt32() == reader2.ReadInt32());
        public override void VisitString(MetaString type) => equals = (reader1.ReadString(type.Count) == reader2.ReadString(type.Count));

        public override void VisitPadding(MetaPadding type)
        {
            reader1.Skip(type.Count);
            reader2.Skip(type.Count);
        }

        public override void VisitStruct(MetaStruct type)
        {
            foreach (var field in type.Fields)
            {
                field.Type.Accept(this);

                if (!equals)
                    break;
            }
        }

        public override void VisitArray(MetaArray type)
        {
            CompareArray(type.ElementType, type.Count);
        }

        public override void VisitVarArray(MetaVarArray type)
        {
            int count1, count2;

            if (type.CountField.Type == MetaType.Int16)
            {
                count1 = reader1.ReadInt16();
                count2 = reader2.ReadInt16();
            }
            else
            {
                count1 = reader1.ReadInt32();
                count2 = reader2.ReadInt32();
            }

            equals = (count1 == count2);

            if (!equals)
                return;

            CompareArray(type.ElementType, count1);
        }

        private void CompareArray(MetaType elementType, int count)
        {
            for (int i = 0; i < count; i++)
            {
                elementType.Accept(this);

                if (!equals)
                    break;
            }
        }
    }
}